This invention relates to a method and apparatus for treating volatile organic compounds (VOCs), air toxics, and odors in air emissions. A biofilter is a relatively new biological treatment device to convert VOCs and odor to carbon dioxide and water using biologically active soil, compost, or biofilm on a filter media. The existing biofilters have many drawbacks including frequent clogging and uneven distribution of water and air in the existing biofilter media. Water, nutrients, and air pass through only channels in the existing biofilter media using a limited volume of the media. Clogging often requires labor or energy intensive backwash or frequent replacement/turnover of the media. The object of the present invention is to develop an improved biofilter system that effectively treats VOCs, air toxics, and odor in air emissions by uniformly distributing nutrients, water, air pollutants, and oxygen to biomass grown on the entire volume of media and by eliminating frequent backwash or replacement of media.